================
@@ -2627,6 +2629,93 @@ SDValue DAGCombiner::foldSubToAvg(SDNode *N, const SDLoc
&DL) {
return SDValue();
}
+/// Try to fold a pointer arithmetic node.
+/// This needs to be done separately from normal addition, because pointer
+/// addition is not commutative.
+SDValue DAGCombiner::visitPTRADD(SDNode *N) {
+ SDValue N0 = N->getOperand(0);
+ SDValue N1 = N->getOperand(1);
+ EVT PtrVT = N0.getValueType();
+ EVT IntVT = N1.getValueType();
+ SDLoc DL(N);
+
+ // This is already ensured by an assert in SelectionDAG::getNode(). Several
+ // combines here depend on this assumption.
+ assert(PtrVT == IntVT &&
+ "PTRADD with different operand types is not supported");
+
+ // fold (ptradd undef, y) -> undef
+ if (N0.isUndef())
+ return N0;
+
+ // fold (ptradd x, undef) -> undef
+ if (N1.isUndef())
+ return DAG.getUNDEF(PtrVT);
+
+ // fold (ptradd x, 0) -> x
+ if (isNullConstant(N1))
+ return N0;
+
+ // fold (ptradd 0, x) -> x
+ if (isNullConstant(N0))
----------------
ritter-x2a wrote:
There is an `assert(PtrVT == IntVT)` above and a similar assert in
`SelectionDAG::getNode()` that rules that out (the reasoning for adding the
assert in `getNode` was
[here](https://github.com/llvm/llvm-project/pull/140017#issuecomment-2893168440)).
We can add this condition here as well to emphasize it even more, but to make
the combines truly safe against problems when pointer and index type mismatches
are allowed, we'd also need to handle, e.g., cases where the types of `Y` and
`Z` in the reassociation below don't match (and there are probably more cases
where explicit handling would be required).
https://github.com/llvm/llvm-project/pull/142739
_______________________________________________
llvm-branch-commits mailing list
llvm-branch-commits@lists.llvm.org
https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-branch-commits
